Instrumentation amplifiers are used to accurately measure a variety of test and measurement signals. A medical instrumentation amplifier, for example, may be configured to measure physiological signals, such as electrocardiogram (ECG), electromyogram (EMG), electroencephalogram (EEG), pressure, impedance, and motion signals. Typically, instrumentation amplifiers are constructed as differential amplifiers exhibiting low offset, low drift, low noise, high common mode rejection, high loop gain, and high input impedance. In many cases, instrumentation amplifiers may require careful matching and trimming of circuit components to achieve a high degree of accuracy.
An instrumentation amplifier may be constructed with a discrete time switched capacitor architecture that obtains discrete signal samples. However, a discrete time architecture can produce undesirable aliasing of noise and signals, undermining the accuracy of measurement signals. Alternatively, an instrumentation amplifier may employ a chopper stabilized architecture in which a chopper circuit up-modulates a measurement signal into a higher frequency band to remove noise and offset. A chopper-stabilized architecture may have a limited bandwidth, however, producing a large ripple in the passband. The ripple may make implementation of chopper-stabilized designs difficult in low power applications.